Stable frequency sources, such as clocks, are required for numerous electronic applications. For example, microprocessors need a clock in order to function. Currently, a discrete piezoelectric frequency control device, such as a quartz oscillator, provides a stable frequency signal to integrated circuit electronic components. This hybrid combination of a piezoelectric oscillator together with an integrated circuit, is much larger than the integrated circuit by itself. In order to reduce the total size of an electronic device, the piezoelectric frequency source should be fabricated in the semiconductor substrate, to provide a monolithic, integrated acoustic/electronic device that is much smaller than the hybrid combination.
New technology has emerged which does fabricate the piezoelectric source into a semiconductor to form a monolithic acoustic/electronic integrated circuit. However, when operating at room temperature, the conductivity of the semiconductor reduces the quality factor Q, which in turn degrades the performance of the acoustic device. As a result, such monolithic acoustic/electronic devices have not achieved the high performance, low phase noise, or high Q of the discrete quartz oscillators used in the hybrid circuits.
Therefore, a strong need to improve the performance of piezoelectric semiconductor frequency sources exists. This need is met be providing a constant, low temperature environment, along with electronic feedback circuitry to compensate for fluctuations in temperature.
Similarly, at high temperatures, there is a need for a piezoelectric resonator which is able to function at high temperatures.